1. Field of the Invention
The present invention relates to a tool for recovering debris and other objects from a well, to facilitate cleanout of the well through the wellbore.
2. Description of the Related Art
In drilling a well, a thorough wellbore cleanout operation is generally required prior to installing a solid expandable liner or smart completion. Smart completion generally refers to downhole wellbore completion equipment or tools that are equipped with flow-control devices that can close or partially close a producing interval. Such devices are operated via either hydraulic control lines or electrical control lines from the surface. They are mostly hydraulically operated at the present time in the field.
For any kind of well, the wellbore must be as clean as possible. The very first requirements are that the wellbore will be free of debris or any foreign objects for the purpose of reducing failure risk of running completion, or for reducing potential reservoir damage, or causing blockage to production tubing at the production stage. Therefore it is particularly important to remove downhole objects such as metal, brass, aluminum, cement blocks, pieces of rubber, or debris from production casing. Hereafter, such objects shall be referred to as “Junk”, or “Junks”.
Packer slips are a set of hanging devices that are usually designed to extend out and bite or indent into the base casing as a result of the packer setting force, so that they carry the weight of the packer together with any attached production tubing string that is below the packer.
Production packer generally refers to a device or downhole tool that separates the producing interval exposed to reservoir fluid from the interval above it by acting as a physical isolation barrier. It usually includes packer slips and packer elements which typically are comprised of an elastomeric band, or in some cases, a band which provides a metal-to-metal surface. The packer element generally provides a pressure seal from above to below the location of the device. The packer element is usually set by shifting a built-in mandrel so that the outer diameter of the element becomes larger and is compressed against the casing wall. The packer element is a means for compartmenting a reservoir. It assists in the efficient production of oil or gas from a well having one or more productive horizons. The function of the packer is to provide a seal between the outside of the tubing and the inside of the casing to prevent movement of fluids past this port. Although the expression “production packer” is sometimes referred to as just “packer”, a packer which is not used as a production packer usually does not contain packer slips. Such packers can be deployed below the production packer as an open hole, or cased hole packer, with the purpose of acting as a zonal isolation device.
The heavy junks are typically made of large pieces of packer slips after milling the production packer, or small metal pieces after cutting the window exit, or junks left behind from earlier drilling BHA (i.e., bottom hole assembly). These junks usually fall down or lay on the low side of the hole, and are difficult to circulate out of the hole, in that they generally reside either in highly deviated or horizontal sections of the production casing/liner, or in an open hole below the casing shoe.
Currently there are many types of available downhole tools that can be deployed to perform a junk removal operation, including:
a) core barrel type junk catchers;
b) reverse circulating junk baskets;
c) casing scrappers;
d) casing brushes;
e) string magnets;
f) Well Patroller®;
g) Junk Trapper® by Well Flow International; and
h) Various other systems.
The first two tools mentioned herein are usually used for “fishing” operations in which the “fish” (i.e., junk) may be a lost cone from a tri-cone drill bit, or part of a failed stabilizer or roller reamer, or some other part of the BHA. Such “fish” is typically greater in size than a few inches in diameter. These types of “fishing” tools involve first pushing the “fish” to the bottom of the hole, and then attempting to wash-over or swallow the “fish” by rotating the tool from the surface to cut the formation so that the “fish” is forced into the tool barrel. In the case of using a reverse circulating junk basket, a ball is dropped into the drill string, and it is pumped downwardly, until it lands on its seat inside the tool, so that circulating fluid is diverted out into the annulus between the tool and the formation. The flow then returns via the inner junk basket. The fluid pressure (if any) may help push the “fish” into the basket. On some tools, the front of the basket has a type of catcher device that attempts to keep the big junk closed in. The types of tools described hereinabove are not intended to be effective to catch small to medium size junks or debris.
Some of the tools described hereinabove are typically designed for wellbore cleanout operations that are intended to remove a large amount of small to medium size junks or debris from a cased hole.
Current practice of wellbore cleanout operations often requires multiple trips. However, no assurance is given until a proper drift is conducted to verify that the hole is indeed clean. Also, currently deployed wellbore cleanout BHA is generally less effective, particularly in dirty wellbores.
The commonly used tools such as Well Patroller@ or Junk Trapper® are always designed to be part of wellbore cleanout BHA and are usually spaced out at or near the top of the BHA.
Well Patroller® is a trademark of Specialized Petroleum Services Group Limited Corporation, United Kingdom, for power operated downhole tools used for the drilling of oil and gas. Junk Trapper® is a trademark of Well Flow International for a multi-functional tool used to retrieve a wide assortment of materials left downhole. In general, both tools are downhole filter-type junk or debris collectors which are commonly used in the field.
The effectiveness of the above-mentioned tools has been shown to be very limited from many field experiences, where the junks collected by such tools were often considerably less than that from string magnets, because the very first tool of the BHA was typically a used bit or taper mill that was turned to first encounter the largest of the junks. In such case, the junks were likely to be pushed downhole and even to the open hole below the casing shoe, because the bit or mill is generally not designed to catch such large junks. If the junks passed the bit or taper mill, they could be circulated up some distance and then fall down again during pipe connection time. This may be a particular problem in a high angle cased hole section where it is usually difficult to move junks by circulation alone, specifically with regard to metal junks. As a result, the string magnet often turned to catch some metal junks because of its close proximity, while some of the junks stayed in the wellbore. Some small pieces were trapped in the junk catcher if they were able to travel further up the hole due to hydraulic forces created by a higher than usual pump rate. If it were not possible to establish circulation due to total mud loss environment, then these tools were much less effective to the point of not even being worth operating. This situation may become a challenging task with re-entry workover wells that turn to have many metal junks either left in the hole after milling and retrieving the production packer, or junks left over from a previous drilling operation. Consequently several cleanout runs must usually be performed in order to remove as much of the downhole junks as possible.
The existing wellbore cleanout tools sometimes suffered the dramatic failure of screen or sleeve out body, usually due to a sizable metal junk stuck between the outer body and pre-existing casing. Such condition required the work pipe to be shifted up and down in order to free the tool when it became stuck inside the casing. Eventually the screen or sleeve would fail. In addition, the pressure cup or seal ring made of rubber with a larger outside diameter (i.e., equal to the casing internal diameter or slightly larger than the casing drift) at or near the top of these tools, that is typically designed to divert all return flow through their junk barrels, rarely survived the entire cleanout procedure. This was due in part to severe and prolonged friction forces caused by work string rotation, which led to cup failure.
In the context of the present invention, the expression “work string” refers to a drill pipe string typically, and the wellbore cleanout tools attached at the bottom of the work string. The expression “cup failure” refers to the case where a wellbore cleanout tool that has a rubber device, or “cup” with a slightly larger diameter than the rest of the tool, when the tool is rotated and moving up or down with the work string. The “cup” is acted directly against the casing inner surface as a physical barrier so that the returned fluid (i.e., fluid which is pumping down through the tool) is diverted through the inner chamber of the tool for junk collection. Because of friction and lengthy hours of service, such rubber cup usually fails, wherein it is often broken and sometimes left as junk in the hole.
As a result, more junk may be left in the wellbore, rather than being removed during the wellbore cleanout. Because of this relatively major risk, Well Patroller® or an equivalent tool are rarely run toward the casing shoe, or even close to what may be a dirty hole section where hard metal junks may be present. Consequently this type of wellbore cleanout operation is less effective.
U.S. Pat. No. 3,023,810 discloses a reverse circulating junk retriever. U.S. Pat. No. 4,059,155 relates to a reverse circulating junk catcher with internal magnets to retain metal junks. U.S. Pat. No. 5,682,950 discloses a junk mill combined with a junk collector. U.S. Pat. No. 6,250,387 discloses the principle of currently used well patroller tools made by SPS-AFOS Group Limited, Aberdeenshire, United Kingdom. U.S. Pat. No. 7,497,260 discloses another type of junk removal tool. U.S. Pat. No. 4,296,822 relates to a combination core cutting and retaining tool that can be utilized to retrieve junk from a finished wellbore. U.S. Pat. No. 4,084,636 relates to a junk catcher. U.S. Pat. No. 3,203,491 discloses a junk catcher that utilizes a pressurized fluid that is discharged from downwardly angled outlets in the body of the well. U.S. Patent Publication No. 2009/0126933 relates to a tubular retrieving tool that discharges a pressurized fluid through downwardly declined outlets to flush debris from the annular space surrounding the tool. These patents and publications are incorporated herein by reference and made a part of this disclosure.
I have invented an effective wellbore cleanout tool which avoids the disadvantages of prior art tools, some of which are described hereinabove.